Lineberger has submitted a renewal proposal to investigate the properties of negative ions and their clusters in the gas phase using negative ion photoelectron spectroscopy and ultrafast pump-probe excitation of ionic complexes. With these techniques both the structural information and the reaction dynamics will be investigated for a broad class of systems which are either chemical transients, reactive intermediates, or transition state species. Among the molecules to be studied are organic radicals and biradicals, metals and metal clusters, and transition states for both unimolecular and bimolecular processes. Electron affinities, singlet-triplet splittings, vibrational frequencies, and geometrical information will be obtained. Ortho, meta, and para forms of benzyne (C6H4) will be synthesized using stereochemical control. Unimolecular processes investigated by ultrafast methods include the 1,2 hydrogen shift in vinylidene to form acetylene. The dynamics of ions in a solvent cage will also be extended by following the appearance of products of cage disintegration as well as solvent reorganization following electron transfer in partially solvated ions. One goal of these studies is to increase the quantitative understanding of the processes driving the simplest chemical transformations. By studying the chemical transformations of molecules which are both isolated as well as surrounded by solvent species, Lineberger will be able to demonstrate the effect that different solvents have on reactivity as well as on the rates at which these reactions proceed.
